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Astronomy: The summer night sky

Astronomy: The summer night sky

AT any time of the night, in any season, when the sky is free from pollution, mist droplets or city lights — or glow of any other kind (even the lunar) one can see around three thousand stars of variant brightness. This of course does not include those multitudinous stars that lie embedded in that arm of the Milky Way, our own parent galaxy that passes far overhead from the north of the sky and snakes across the southerly direction. It happens to be one of the seven ‘arms’ of the milky way that originate from the galactic nucleus, some terminate approx halfway, much like a pin wheel.

All seasons have their specific stars and constellations, which verily appear all year round but are the signature to that particular season. In the remaining seasons, the “unseasonal” ones appear late, or even early but their shapes, angles or position, called aspect in the sky, are distorted, occasionally not easy to recognise or identify. This is because of the shifting position of the Earth as it goes around in its orbit around the Sun.

In observational astronomy, however, the two main seasons are summer and winter. All stars and constellations are lumped together accordingly. We are into the peak of summer season and what a magnificent parade of brilliantly stars and lovely constellations that populate the dark vault! Take the king of them all, Orion. Then, Gemini the twins; the stately Seven Sisters, or Pleiades, a conglomeration of some 200 stars that came into being from a single cloud of gas and dust called nebula only 50 million years ago just after the time when the great dinosaurs had recently been wiped out from the face of the Earth. Hence it is a young constellation. Then there is Aldebaran, the eye of the bull, and many more of equal eminence.

The winter constellations also hold in their mysterious embrace hundreds of thousands of far away galaxies each consisting of billions of stars gravitationally bound to their respective nucleus. To view these distant galaxies one must possess a ‘pretty good’ telescope besides a quality camera to capture the faintest of faint images, plus the patience and perseverance that goes with the rigours of the night long vigil. The knowledge of the night sky is the first essential, though.

All told it is every bit likely that despite a fine telescope you will barely catch a feeble image of the distant galaxies. That as an opaque dot, with many such, tiny, elongated streaks trying scattered nearby.

For a naked-eyed viewing of a galaxy the best bet is the Andromeda Galaxy, way up in the northern region of the sky. It is fixed like a hazy, opaque patch in the constellation of the same name. However, for those residing in the southern hemisphere (Australia, South Africa, South America, etc.) they are lucky in that they can watch two satellite galaxies called the Small and the Large Magellanic Clouds. The Milky Way is their Parent Galaxy.

Now the prevailing summer skies; the story of the night sky is not complete without the summer sky. Less populated than the winter sky, it has some prominent constellations and stars such as, Vega (the fourth brightest of them all) Altair, Deneb, and Antares, etc.

This catapults us to the highly graphic constellations popularly named as the Summer Triangle. The Summer Triangle is actually not one but three constellations so named because three of its main stars head to form a huge triangle, covering a large portion of the sky. The names of the individual constellations in the summer Triangle are Lyre, Cygnus and Aquila.

Each of them contains at least one bright star universally acknowledged for its luminosity and beauty. For instance, Lyra (or Lyre) has the brilliant star Vega; Cygnus has the lovely star Deneb (or Zainab in Arabic) and Altair (the bird, again in Arabic) is in the constellation Aquila.

The star Deneb may be found in a straight line drawn from the two stars of Ursa Major; while Altair in Aquila has a star chaperoning on either side of it. The cross in Cygnus is quite distinctive. Of all these stars, Deneb is the faintest as it is much more distant but far more luminous than Vega or Altair. It is 60,000 times more powerful than our Sun.

The easiest way to find the Summer Triangle is to look for it during summer months around the zenith of the sky. The Ominous Triangle is there for you to locate easily. Look first for the individual constellation, then those respective prominent stars. Late at the night time there is the Scorpio which takes up thousands of square light years, and which has special attraction for those born under the Scorpion sign, since it is a part of the zodiac. Much has been said about astrology and the vanity of those hankering after their so called birth signs in my previous columns; so, the less said about them the better.

A small telescope will reveal many colourful nebulae — those unpretentious star nurseries where stars are born and reared until they drift apart and live a life of their own with their individual families. And a whole lot more. You never know you might end up discovering a comet or two and having them named after yourself, bringing honour to your family, friends, above all our beautiful country like so many of them elsewhere in the past. Good bye and God bless. n

The writer is a former planetarium head and an internationally renowned astronomer and astronomy writer and can be reached at [email protected]

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